Recently, solid-state imaging elements for mobile cameras mounted on cellular phones, etc. have been reduced in size: solid-state imaging elements such as CCD devices, CMOS, etc. that have a pixel size of 2 μm or smaller are used.
A practically useful imaging lens, which has capabilities matching a solid-state imaging element having such a very small pixel size, is manufactured by using four lenses, and aberrations of these lenses need to be sufficiently corrected.
One example of an imaging lens that uses four lenses is disclosed in Patent Literature 1.
Patent Literature 1: Unexamined Japanese Patent Application KOKAI Publication No. 2002-365529